RHINOCEROS. 587 



In the discontinuity of the enamel covering the molars, the Toxodon 

 differs from all known Pachyderms, and manifests a slight approach 

 to the Brut a. 



214. Elasmotherium{\) . — This name has heen given to an extinct 

 Pachyderm with rootless molars, surpassing the Toxodon in size, and 

 of which only the lower jaw and its dentition are as yet known ; but 

 the characters of the teeth are sufficiently remarkable to call for 

 notice here. The molar teeth of the Elasmotherium are five in 

 number in each ramus of the jaw, the anterior one being very 

 small ; the penultimate one is the largest, measuring three inches 

 in the antero-posterior diameter, and two inches in the transverse 

 diameter of the crown. The enamel is remarkable for its beautiful 

 undulating folds ; but its general disposition most resembles that 

 in the inferior molars of the Rhinoceros (2). The teeth of the 

 Elasmotherium differ from those of the Rhinoceros, and resemble 

 those of the Horse in the great depth to which they are implanted in 

 the jaw, before being divided into roots : the socket of the penul- 

 timate grinder extends, in fact, to the lower margin of the jaw 

 without any indication of partitions for the lodgment of fangs : 

 there is no trace of incisive teeth in the portion of symphysis which 

 is preserved, and which extends a little more than three inches in 

 advance of the first small molar. The above account is taken from a 

 cast and the description by Cuvier, in the * Ossemens Fossiles', 4to. 

 tom. II. pt. i, p. 96. The original is preserved in the Museum of 

 Moscow, and is unique ; it was discovered in the frozen drift oe 

 diluvium of Siberia. 



215. Rhinocerotidcs. — ^The present family of anisodactyle Pachy- 

 derms includes the typical Rhinoceros, the extinct Acerotherium which 

 had no horn, and the equally hornless small existing genus Hyrax. 

 The essential characteristics of the dentition of the genus Rhinoceros 

 are to be found in the form and structure of the molar teeth. In the 

 first place, they differ essentially from those of the Horse or Elasmothere 

 by being implanted by distinct roots. In the upper jaw the crown is 



(1) eXatTfia a plate, drjpioy beast : in allusion to the plicated plates of enamel in the 

 substance of the molar teeth. 



(2) Compare figure 12 in Plate 136, with p. 3, fig. 11 in Plate 138. 



